Note: Descriptions are shown in the official language in which they were submitted.
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h THOD of MDSTRO 1fl EDP'
This invention is in the field of seeds, and in particular the treatment of
seeds to ensure
that the seeds do not germinate or reproduce, and to degrade residual
chemicals and
sterilize pathogens that may be present in a seed sample.
BACKGROUND
Destruction of seeds to prevent germination and reproduction thereof is
presently an issue
of concern. Genetic modification of seed has received an adverse reaction from
a
significant portion of the public, concerned about detrimental effects if
viable forms of
modified seed were to escape into the environment. The possibility that
experimental
seed could escape into the environment is of such concern that companies
engaged in
research into such seeds wish to be able to ensure to the public that such
escape will not
occur.
As a result, companies engaged in seed research cannot simply discard
experimental seed
that is not needed, but must ensure that the germinal viability of the seed is
destroyed.
Grinding or crushing seed using methods of the prior art cannot guarantee that
some
germination can remain viable. Small seeds, such as canola, are especially
difficult to
pulverize effectively to destroy viability. in addition, grinding or crushing
methods are
time-consuming, and it is difficult to be confident that the seeds have been
adequately
destroyed without resorting to additional testing procedures to determine
whether any
viable seed remains or not. Incineration processes are effective in producing
100%
deactivation, but the burning process creates undesirable by-products and
emissions are
difficult to control and pose a potential environmental hazard. In addition,
incineration is
expensive in terms of energy costs, and typically makes use of non-renewable
energy
sources such as natural gas or other fossil fuels. The use of these energy
sources further
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contributes to greenhouse gas emission, as well as to the depletion of finite
energy
reserves, and is therefore a less than desirable solution.
Although genetically modified seeds are most in the public awareness, it is
contemplated
that it might also be desired to destroy other conventionally bred seeds, or
undesirable
seeds found in nature such as various weeds.
Of additional concern is the effect that residual chemical agents such as
herbicides and
pesticides, commonly applied to commercial crops, may have on the environment
and the
health of animals and humans. Residues may remain in seed samples increasing
the risk
to human or animal health when seed products are either consumed or handled.
Likewise, seed samples can harbor pathogens such as molds, bacteria or viruses
and other
similar biologies that in some cases pose a threat to human health. A known
hazard in
the field of agriculture is the exposure of farm workers to molds that
propagate in seed
over time under suitable conditions. Exposure has been associated with
asthmatic
reactions, and lung infections that can lead to scarring and permanent damage.
Farm
workers account for 30% of adult respiratory disease and yet only comprise 1%
of the
population (Storm & Genter (1995), AG-MED-6, North Carolina Cooperative
Extension
Service).
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a method of destroying
seed that
ensures that the seeds will not reproduce. It is a further object of the
present invention to
provide such a method that transforms the seed into a product that may be
environmentally safely disposed of
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It is yet another object of the present invention to provide a method of
degrading
chemicals such as herbicides and pesticides that may be present in a seed
sample in order
to make the seed safer for handling or consumption.
It is a. farther object of the present invention to provide a method of
sterilizing pathogens
such as viruses, bacteria, fungi and protozoans and the like, which may be
present in a
seed sample.
The invention provides a method of destroying seeds. The seeds are heated to
substantially 95 C and maintained at that temperature for substantially 30
minutes.
Preferably a combination of steam and microwaves is used to maintain the
temperature.
Dampening the seeds, with steam at the intake end of the process helps the
microwaves
work more efficiently in maintaining temperature.
Additionally, the seeds are treated with ozone. Ozone is a reactive species of
oxygen,
well known in the art to degrade chemical compounds as well as to denature
proteins and
sterilize pathogenic agents. The ozone, in combination with the steam and
microwaves is
operative to degrade residual chemicals, and to deactivate the seeds and any
associated
pathogens present in the seed sample.
An auger conveyor carries the seed through the process. Temperature sensors
monitor
the temperature of the seeds and, control the speed of the auger so that the
seeds are
maintained at substantially 95 C for substantially 30 minutes prior to exiting
the output
end of the auger conveyor. The auger continuously agitates the seed to provide
substantially even exposure of all the seeds in the sample to the steam.,
microwaves and
ozone. Conveniently the invention may also include ozone sensors to monitor
ozone
levels in the seed sample such that a level of ozone effective to degrade
residual
chemicals and deactivate associated pathogens is present.
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Using the controlled speed auger, the process is continuous, allowing for
considerable
volumes to be processed without intervention or labor requirements, such that
automatic
oversight of the process is possible.
DESCRIPTION OF THE DRAWINGS.-
White the invention is claimed in the concluding portions hereof, preferred
embodiments
are provided in the accompanying detailed description which may be best
understood in
conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numbers, and where:
Fig. I is a schematic side view of an apparatus for practicing a method of the
invention.
Fig. 2 is a schematic side view of a storage container or silo, where ozone
treatment is
performed following the treatment of seeds with steam and microwaves. The
dashed'
arrow shows the direction of flow of the drying air and ozone.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS:
Fig. 1 schematically illustrates an apparatus 10 for practicing a method of
the invention
for destroying seeds to prevent further germination and reproduction from
them. The
seeds are placed into a hopper 1, where steam at 250 - 400 C from a boiler 5
and water
from a water source 6 are added to heat and dampen the seeds.
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The seeds flow from the hopper into a steam chamber 3. Steam is conducted from
the boiler 5
into the steam chamber 3, thereby further raising the temperature of the seed
and further wetting
the seed somewhat.
A shredder roller 9 may be placed in the bottom of the hopper I to break up
the seed surface and
allow the steam to penetrate the seed more readily. Some seeds are known to
have less
permeable outer skins that resist dampening, and breaking up the surface helps
the steam to
penetrate.
At the bottom of the steam chamber 3 the seed flows into the intake of an
auger conveyor 7. The
auger conveyer 7 comprises a tube that provides an enclosure that can be
sealed, as well as an
internal auger, which rotates to move the seeds through the interior of the
enclosure from the
intake end to the discharge end. Further steam from the boiler 5 is added near
the intake of the
auger conveyor 7. At this point the temperature of the seed has been raised to
near 95 C.
Temperature sensors 13 begin to monitor the temperature of the seeds.
Microwave generators 11
further heat the seeds. Once the seed treatment temperature reaches
substantially 95 C, a timer
mechanism adjusts the rotational speed of the auger such that the seed
temperature is maintained
at substantially 95 C or higher for substantially 30 minutes prior to seeds
exiting the auger
conveyor.
Steam could also be used to maintain the temperature of the seed, for example
by encircling the
auger with steam lines. It is however preferred to use a series of microwave
generators I I to
maintain the seed temperature at substantially 95 C or higher during the
entire time that the
seeds are in the enclosure tube. The microwaves work efficiently on the
dampened seeds to
economically maintain the required temperature, and add their own destructive
effects to the
process.
If the temperature of the seed in the auger conveyor 7 is sensed by the
temperature sensors 13 to
be dropping, the auger speed can be reduced so that the seed moves slower
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through the auger conveyor 7, and thus receives more heat from the microwaves.
In this
manner each seed is maintained in the auger conveyor 7 for about 30 minutes,
and is
maintained at the required substantially q5 C or higher temperature while it
is in the
auger conveyor 7. in addition to being effective to inactivate seeds such that
they are no
longer capable of germination, the treatment of seeds as described above is
known in the
art to be an effective method to substantially reduce the number of viable
organisms such
as viruses, bacteria, fungi, protozoa and the like.
The invention further comprises an ozone source 15, connected to the tube in
proximity
of the intake, such that ozone is directly injected into the tube at the
beginning of the
treatment process so that the seeds are subjected to microwaves and ozone
simultaneously. As ozone is well known as being effective to inactivate
pathogens such
as viruses, bacteria, fungi and protozoa and the like, the use of ozone in the
apparatus of
the invention augments the sterilizing effects of the microwaves and steam.
Conveniently, ozone sensors 17 may be included to monitor ozone levels in the
enclosure. The output of the sensors can be used via a control mechanism to
vary the
amount of ozone injected into the enclosure, or to vary the speed of the auger
conveyer 7,
such that seeds are treated with a sufficient concentration of ozone, for an
adequate time,.
such that the ozone further augments the inactivation of seeds, as well as to
substantially
degrade herbicides and pesticides, as well as to substantially inactivate
pathogens present
in the seed sample.
Ozone is further effective to chemically inactivate pesticides and herbicides
associated
with the seed sample. It has previously shown for example that strong oxidants
such as
peroxide or ozone are effective in inactivating the herbicide 2,4-D (Alfano et
al., 2001,
Chemical Engineering Journal, 82, 209 - 218).
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In the present case, experimental tests were performed to test the method of
the invention.
Specifically, 220,000 lbs of canola seed: were treated for 30 min at 95 'C.
After
treatment seeds were tested for germination rates, as well as for the presence
of the
pesticide thiamethoxam. The results of the experiments showed that the rate of
germination was zero, and that thiamethoxam was reduced by more than 100-fold,
in the
treated seed sample. In the experimental tests ozone concentrations of 1500
ppm were
used. It is possible with currently available ozone generation systems to
achieve ozone
levels of 5000 ppm or higher.
Therefore, the data presented herein, when combined with prior studies,
indicates that
ozone is effective to substantially degrade herbicides and pesticides that may
be
associated with seed samples. The data further demonstrate that the invention
is effective
to render seeds inactive such they are no longer capable of germination. Thus,
once the
treated seeds exit the auger conveyor 7, seed viability is effectively zero.
As a result, the
treated seeds exiting the auger conveyor 7 can be safely disposed of. In fact
the treated
seeds can be readily composted, and sold if desired.
The process is continuous, and requires no intervention. Conveniently, sensors
and
control mechanisms may be included to monitor temperature and ozone
concentration in
the enclosure. The outputs from the sensors are sent to control mechanisms
which vary
the speed of the auger conveyer 7 in response to temperature and ozone levels,
so that
seeds are treated for a time sufficient to effectively inactivate seeds, and
substantially
reduce the levels of pathogens, herbicides or pesticides in the seed sample.
Seed can be fed into the hopper 1 continuously through another auger conveyor
sealed to
the cover of 'the hopper I. Steam is restricted from escaping through the
second auger
conveyor tube by the auger and the seeds in the tube. The hopper 1 could also
be sized to
contain a large batch that seldom requires filling. The destroyed seeds can be
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conveniently be transported away continuously, or collected in a container 20
and
removed or disposed of in batches.
Alternatively, instead of or in addition to, introducing ozone into the tube
of the auger
conveyor 7, the seeds may be discharged from the auger conveyor 7 into a
separate
container such as'the conventional storage silo 19, as illustrated in Fig. 2.
The storage
silo 19 can be pre-filled with ozone at the desired concentration of 100 -
5000 ppm. As
the seeds fall through the ozone atmosphere, the ozone will have access to the
seed
surfaces such that the sterilizing properties of the ozone are realized.
Providing ozone in
the interior of the silo 19 also serves to sterilize the inside walls of the
silo, preventing
contamination of the seeds.
The auger conveyor 7 can be, adapted to discharge the seeds into a plurality
of silos 19
such that the continuity of the process can continue uninterrupted as the
silos 19 are filled
and then emptied intermittently.
Further, a seed dryer 21 might be desirable to dry the seed material, which is
damp from
exposure to steam and water, if it is to be stored for any length of time
prior to disposal.
The drying process can be initiated either during or after filling the silo
19. Conveniently T,
ozone from an ozone source 15 is mixed with air from an air inlet 23 and the
air: ozone
mixture is passed through the seeds in the conventional drying process, and
out through a
vent 40.
By providing ozone during the drying process, an advantage is gained in that
ozone will
prevent the growth of any contaminating organisms during the time the seed is
being
dried for further processing or storage.
The foregoing is considered as illustrative only of the principles of the
invention.
Further, since numerous changes and modifications will readily occur to those
skilled in
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the art, it is not desired to limit the invention to the enact construction
and operation
shown and dcscribed$ and accordingly, all such suitable changes or
modifications in
stmctuxe or operation which may be resorted to are intended to fall within the
scope of
the, claimed invention.
